简单工厂模式

import java.util.Scanner;class Operation {public double numberA;public double numberB;public double GetResult() {double result = 0;return result;}public void setNumberB(double numberB) {this.numberB = numberB;}public double getNumberB() {return numberB;}public void setNumberA(double numberA) {this.numberA = numberA;}public double getNumberA() {return numberA;}}class OperationAdd extends Operation {public double GetResult() {double result = 0;result = getNumberA() + getNumberB();return result;}}class OperationSub extends Operation {public double GetResult() {double result = 0;result = getNumberA() - getNumberB();return result;}}class OperationMul extends Operation {public double GetResult() {double result = 0;result = getNumberA() * getNumberB();return result;}}class OperationDiv extends Operation {public double GetResult() {double result = 0;result = getNumberA() / getNumberB();return result;}}public class StaticFactory {public static Operation createOperate(String operate) {Operation oper = null;if (operate.equals("+")) {oper = new OperationAdd();}if (operate.equals("-")) {oper = new OperationSub();}if (operate.equals("*")) {oper = new OperationMul();}if (operate.equals("/")) {oper = new OperationDiv();}return oper;}public static void main(String[] args) {while (true) {Scanner input = new Scanner(System.in);String numA = input.next();String op = input.next();String numB = input.next();Operation oper;oper = StaticFactory.createOperate(op);oper.numberA = Integer.parseInt(numA);oper.numberB = Integer.parseInt(numB);double result = oper.GetResult();System.out.println("= " + result);}}}